Fuel injector



F65. 1942. M. J. MURPHY 2,272,094

FUEL INJECTOR Filed Kay .10, 1937 2 Shuts-Sheet 1 J4 INVENTOR.

Moyes J. Murphy BY 7 f ATTORNEY.

Feb. 3, 1942.

M. J. MURPHY FUEL INJECTOR Filed May 10, 1937 2 Sheets-Sheet 2 'FIIS E F I I3 E INVENTOR. Mag/es J Murphy ATTORNEY.

Patented Feb. 3, 1942 rum. mscc'ron Moyes J. Murphy, Milwaukee, Wis, alsignor to Murphy Diesel Company, a corporation of Delaware Application May 10, 1937, Serial No. 141,674

SCI/aims.

My invention relates generally to means for introducing fuel into internal combustion engines, although it likewise concerns any discharge device for releasing fuel under pressure in a predetermined manner. A typical arrangement of a fuel injector in an internal combustion engine wherein the injector has some of the same physical characteristics as the fuel injector of this case is disclosed in my copending applica tion Serial No. 743,339, filed September 10, 1934, entitled "Fuel injection apparatus," and of which as to som matters this application is a continuation.

In the discharge of liquid fuel, such as fuel oil, from a conduit for combustion, it is important to have the discharge as carefully regulated and metered as possible, since the eillciency of combustion is directly dependent upon the character of discharge of fuel from its conduit. This is particularly true in the case of internal combustion engines employing compression ignition, since the character of the fuel discharge largely controls the eliiciency of operation and performance characteristics of the engine. In larger engines, where the absolute quantity of fuel handled per cycle is large, an error of a certain magnitude is proportionately insignificant and inconsequential. and variations in engine performance ascribable to fuel error are not especially noticeable or objectionable; but when the engine size is reduced and the absolute quantity of fuel per cycle is correspondingly reduced, then an error of comparable magnitude is far larger proportionately and adversely affects the operation and efficiency of combustion to a serious degree.

It is therefore an obiect of my invention to provide a fuel iniector which is capable of providing an emcient release of fuel for combustion.

Another object of my invention is to Provide means for dispensing relativelyasmall quantities of fuel per cycle, with injection errors which are also relatively small.

A further object of my invention is to provide an injector which has excellent characteristics when dispensing relatively small quantities of fuel.

Another object of my invention is to provide an injector which conforms generally to good engineering practice yet has improved characteristics.

Another object of my invention is to provide an improved means for releasing fuel under pressure from its conduit,

An additional obiectlof my invention is to provide means for releasing fuel according to a predetermined cycle of'operation. p

The foregoing and other objects aresttained in the embodiment of the invention illustrated in the drawings, in which- Fig. l is a cross-section on an'axial plane. showing a fuel injector in accordance with my invention, certain portionsbeing shown in side elevation and part of the figure being broken away to reduce its sire; L

Fig. 2 is a cross-section similar to Fig. 1 but showing the terminus of the fuel injector to an enlarged scale;

Fig. 8 is a cross-section the plane of which is indicated by the line 8-3 of Fig. 2, a portion at" the figure being broken away to reduce its In its preferred form, the fuel injector of my invention comprises an injector body having a bore and an outlet from the bore, combined with a plunger reciprocable in the bore to discharge fuel through the outlet, and having a means, such as a spring-loaded check valve operated by the fuel, for repeatedly interrupting the discharge of fuel through said outlet during a single reciprocation of said plunger.

Although the fuel injector of my invention is well adapted to use under various different circumstances, and in fact wherever fuel is to be released from a conduit according to a predetermined cycle of operation, it finds especial adaptation in conjunction with an engine operating upon the-compression ignition cycle as described in my copending application hereinabove identified. and in the present instance it itsnlgzlwise disclosed in such an embodiment as In an cosine installation, the injector body iisseatadinasuitablesocketintheengine head (not shown), so that the depending portion I of the body is in proximity to the combustion chamber. Within the injector body i there is an injector barrel 8 having a central bore 0 therein within which reciprocates a plunger ii. The plunger is suitably guided and extends to a cross-head I! carrying roller cam followers If at its opposite forks. Both of the followers II are urged to respond to the contour of driving cams M on cam shafts II, by reason of a plurality of nested coil springs I I abutting a cap il suitably fixed with respect to the injector body 8. During rotation of the cam shafts It the cams ll simultaneously lift the rollers l8 and the cross-head it against the Relief passages 24, communicating radially" with the passage 22, are likewise in communication with the bore 9 through spiral grooves 25 provided in the plunger H... Rotation of the plunger H by suitable mechanism varies the time of cut-off of fuel injection which may be established at any appropriate or selected point I to terminate the injection period. But. prior to cut-off, fuel which has been trapped within the bore 9 due to covering of the passages 23 and fil by' tii descent of the plunger, is therefore metered" as i'tfis segregated from the general body of fuel in the paissageji. i- This metered duanigity df ffuei is expelled from tii bbr Sby 'furtherdescentof the plunger ll, through an outlet 28 which preferably is aeylin- '-'di'iial bore coaxial withthe bore 9 and piercing fa rinmb1e2 si-"*me tliimble-is held in the end of the injector bbdy t by a threaded cap 3l'engag ingthebody 6. The diameter of the passage 28 is made relatively smalipand its length isQalso -relatively sl'lort. Under preferred operating con- 'ditions were is turbulent 116w ti'flerethroil gh. At the terminus of the outlet fl and formed in the thimble =29, there is valve ,et 11 which prefraliiy is conical 'incontour'aii li is coaxial with F the outlet II.

Adapted to rest upon the valve seat 32 is a check valve, preferably in the form of a ball 33, f relatively small diameter and urged upon the seat 32 by a coil spring 14 seated within a recess 4'! wltliinthe cap 31. The forced the spring is exerted through a centraiizer l1 contacting the ball 33 and -freely slidable within the recess 5 irbecause ofample clearanceprovided between the walls or therecess'and the centralizer. The centraliser 11 is provided with a passage ll "therein. so that fuel passing the ball I! flows past the square head of the centralizer andboth around the body thereof and through the passage 38 intoa dischargechannel 3Q coaxial with the outlet ll, finally communicating with injection orifices I, usually six in number, arranged equidistantly and radially about the discharge passage 38 as a center. 1 "The strucif 'e so far described. adjacent the --clieck valve 38, is shown in enlarged detail in Fig. 2, since the proportions of the ball II. the

channel 28. the spring I and the centralize:- II

' are such tliatdur'ing'the norinal reciprocatory movement or plunger ll within the bore 0. and particularly during the injection period of the operating cycle except possibly at highest engine speeds, the valve is shatters upon its seat 32. The elastic fuel flowing through the channel 28 dislodges the ball II from its seat just far enough to release the fuel. Movement of the check 33 is accompanied by translation of the centralizer 31 and compression of the spring II, but the proportion. elasticity and strength of the parts are such that the spring 34 overcomes the force of the initial discharge pressure of the fuel and resents the ball valve 3! upon the valve seat 82. After such initial reseating. the subsequently increased pressure in the channel 28. due to further discharging reciprocation of the plunger ll, again unseats the valve 33, recompressing the spring 34. This alternate unseating and seating of the ball 33 during the injection period preferably occurs repeatedly and with such rapidity as to give rise to an audible buzzing sound when the injector is discharged at low engine speeds; hence the ball I! is referred to herein as fluttering. vibrating or chattering upon its seat with audible frequency.

The frequency of vibration varies with engine speed, and the system may be such that the frequency increases from an audible one at low engine speeds to a super-audible one at high engine speeds. The decreasing amplitude of. vibration with increasing frequency may even be so related ioengine speed that adjacent maximum engine speed the amplitude is virtually zero; that is, the

2 check valve may remain continuously open during the injection interval. L

The vibration characteristics are ,aflected by manyfactors other than the elasticity of the fuel itself and the unbalance of the check valve 33.

* For example. the length and the volume of the fuel column defined by passage 2! are kept rela- L tively small to reduce pressure reflection waves and surges therein and to maintain a relatively high natural resonance therein. Similarly, the

length and the volume of the fuel column between the check valve II and the orifices H are kept relatively small to reduce the effect. of fuel It is emphasized that, the

"centralizer I1 and the spring 3 are of. small mass and are out of frictional contact with the surrounding walls to avoid the effect of sliding friction and large inertia forces.

The result of such operation of the check 83 is to provide an interrupted or noncontlnuous discharge of fuel from the passage 18 into the outlet II, so that for a given quantity or volume of fuel metered by entrapment within the bore 9, while the average velocity of efllu'x of the fuel through the ball check is probably the same in reference to a given injection period as though no chattering occurred. nevertheless the average fuel velocity during the time each individual discharge is taking place is considerably more than would be thecase if the ball 13 remained continuously unseated, Hence, it is found in practice that a relatively small quantity "of metered fuel can be introduced into the cylinder at considerably more than would be its velocity if the ball 33 did not chatter. Improved practical results in engine operation are thus attained.

For example, with a continuously open check valve and a high engine speed, let it be assumed that satisfactory injection occurs. But as the engine speed is reduced, theinjection pressure also reduces, but at the 2.7 power of the engine speed. At idling speed, the injection pressure is therefore so low as to give very poor injection. If the injection pressure at idling speed is arbitrarily increased to a minimum satisfactory value, then at high or normal engine operating speeds the injection pressure is excessive-in a representative case being about 12,000 pounds per square inch. Yet when the design is changed to aflord a vibrating check valve and interrupted injection, particularly at idling speeds, entirely satisfactory idling injection is obtained without seating and unssaungr pai hfi l mbn increasing the linemen preSShre' above '1j000 pounds pershuar men at high iii-"normal engine jperatink I M The arrangement of the-outlet s amans in y during" the disof the fuel is V (eseeeisu c H .8 F, period; so tii'ateachiriiectipn is realign. series of successive purts. ,or bursts 6fiiiLeach slu'g r01- lowl'ngtlie preceding one with great rapidity, yet with a definite interval therebetween.

This repetitive stream of bursts of fuel which emerges from the apertures 4| during the injection period not only is materially different from the standard continuous injection, in the shape of the gas envelope surrounding the central fuel core and in the streamlined shape of the fuel particles themselves, but likewise varies materially in penetrating power and dispersion within the combustion chamber. The different effect is particularly noticeable at low engine speeds or during prolonged engine idling, since the velocity of elllux of the individual fuel bursts is considerably higher than it would be if there were a continuous discharge or injection of a comparable amount of fuel during the same injection period. The practical results are, materially improved characteristics during operation on minute quantities of fuel, and good penetration and excellent combustion even though idling of a relatively small engine is prolonged.

In the present instance, the beneficial and improved results are attained without materially altering the design of the injector so far as its general aspect is concerned, but are attained primarily by designing the passage 28, the valve seat 32, the check valve 33, the spring 34 and the centralizer 31 with such proportions and relationships that a vibrating system is provided to afford a means for interrupting or repeatedly severing the stream of fuel being injected during the injection period. This interrupting means, being operated by the fuel itself, and entailing the use of only a few very simple parts, is capable of operation without difliculty over protracted periods.

As illustrative of a typical embodiment of my invention in an engine cylinder of about 170 cubic inches volume, by which the results herein described are attained, the drawing of Fig. 2 shows the plunger ll having a diameter of .4 inch. The passage 28 has an internal diameter of .062 inch, while the total length of the thimble is about .75 inch. The valve seat 32 is a cone the included angle between elements of which is 90", having a minimum diameter of .078 inch and a maximum diameter of .098 inch. The material is S. A. E. No. 52100 steel and is treated to attain a Rockwell hardness of 063-65. The ball valve 33 itself is .125 inch in diameter and is held to a limit of sphericity of .000025 inch, being made of high chrome steel and hardened. The centralizer 31, which abuts the ball 33, is .406 inch in overall length, has a maximum diameter of about .24 inch and a body diameter of about .175 inch. The conical seat 42 thereof has an included angle between elements of and , central {having **"fliepdlled 3 int a mast rs! Jim. at

10 outside diameter "'whih ii lpngtjl Y V A The'ftotalnumirriqt na isi a h 11 ms j s Ti 1 8 1.?

that 1 the was essentialist s tellites,

10.3 pounds. So far as the cap 3| is concerned, the recess 36 has a diameter of .261 inch, while the passage 39 has a diameter of .062 inch, and the outlet orifices ll, of which there are six, are each .01 inch in diameter.

The proportion of the parts and their relative arrangement as disclosed herein provide a vibrating check valve system producing consistent interruption of the injection fuel during the injection period.

I claim:

1. In a fuel injector having a pump barrel and a plunger working in said barrel, a spray nozzle having a discharge orifice of constant area, a check valve controlling the passage of fuel from said barrel to said nozzle, and closing means for said valve, means promoting a chattering action of said check valve comprising an outlet from said pump barrel of reduced volume and the check valve and its closing means being of small mass to reduce their inertia, and means for 40 maintaining substantially undamped the surges traveling from the check valve to the nozzle.

2. In a fuel injector having a pump barrel and a plunger working in said barrel, a discharge outlet from said barrel having a spray nozzle structure at its outer end with a spray orifice of constant area and less than that of the outlet from said barrel, the combination of a check valve intermediate the ends of said outlet, and spring means for closing said valve, said outlet 50 from said barrel to said valve being of an effective volume to keep the fuel column therein relatively small to reduce pressure reflection waves and surges therein and to maintain a relatively high natural resonance therein, said valve and its closing means being of small mass and said parts being so constructed, proportioned, and arranged that said valve is caused to chatter on its seat during the discharging stroke of said plunger, the length and volume of said outlet between said valve and said nozzle being relatively small to reduce the effect of fuel elasticity and maintain substantially undamped the surges traveling from the check valve to the nozzle.

3. In a fuel injector having a pump barrel and a a plunger working in said barrel, the spray nozzle having a discharge orifice of constant area, the combination of an outlet from said barrel so constructed as to reduce the fuel flowing therein to a small stream to reduce pressure reflection waves and surges therein and to maintain a relatively high natural resonance therein, a check valve for controlling the passage of fuel from said outlet, 8. spring for closing said valve, a centralizer cooperating with said spring, the mass of the valve and centralizer being small to re.

ducethelnertiaolthesepu'issaldpartsbelnz so constructed. pr p rtioned, and arranged so thatundertheactionoi'thepressureofthe fuel from said outlet the valve chatter: on its seat, the centrallzer and spring being disposed aheadoithevalvelnasoacebetweensaidvalve andnonlsandactlngtoreducethevolumeof seidspacetoa smell amountsoastoreducethe eflect of fuel elasticity and maintain substantialiy undamped the surges traveling from the check valve to the nonle.

4. In a fuel injector having a pump barrel and a plunger working in said barrel, the combinatlon of a restricted outlet from cold barrel, a check valve controlling said outlet, a centrallzer abutting said valve and spaced from the walls of said body. a spring abutting said centrallser, and anonleoiconstantdischarge areaandlessthan apropos that oltheoutletirornsaldbarrehsaidperts soconstructedmroportionemandarrsnzedasto cause said valve to chatter under the pressure of fuel from said outlet.

5. Inatuelinjectorhavingapumpbarreland a plunger working therein, the combination of a restricted outlet from said barrel, a ball check valve controlling the discharge from said outlet and a discharge passage beyond said valve having an outlet of constant area. and less than that or the outlet from said barrel, a spring in said dlscharge passage imrlna said valve to its seat and a centre-liner interposed between and contactins said valve and spring, the above parts so constructed, proportioned, and arranged as to cause said valve to chatter during a single discharge trom said barrel.

MOYES J. MURPHY. 

